The Sun's Secret
by Frost Destiny Winter
Summary: Reborn is not himself. And Tsuna thinks that his demonic tutor is keeping a secret. A very dangerous secret.


Reborn is not himself. And Tsuna thinks that his demonic tutor is keeping a secret.

Tsuna started to think that there was something really wrong with his demonic tutor after the Arcobaleno trials were finally done. The curse has been lifted and Verde managed to make a formula to make their aging process faster.

The Arcobaleno who grew fond of him over the years started to visit the mansion more often than not and made Tsuna more like a butler than a boss. He was begged, no, threatened to make drinks that would make one blissful enough to ask another. Tsuna gladly accepted this as an excuse from his paperwork.

The doubts started when the Arcobaleno has turned twelve. This is usually the age where puberty starts to kick in. He could only shudder at times when Lal became fiercer and more hard-headed than ever on certain days. Poor Colonello is reduced to a punching bag whenever he tries to flirt with her. But what strike him the most is the changes that his tutor had.

Usually, he would wake up with ten-ton mallet in his head or a gunshot inches away from his skull. Now, he can wake up more peacefully, and do his morning rituals without a demon by his side. Reborn actually became quieter and steered clear of bitter things, which is a miracle itself. Expressos where banned from the kitchen, and most importantly, no one is threatening him to finish his paperwork in an alarming rate.

He thinks that the stress must have accumulated on his dearest tutor, and as a gift, he gave him an all-expense paid trip to somewhere around the world, sponsored by Vongola. In which his tutor agreed rather reluctantly with compromise that Tsuna must call him every night. Tsuna mentally agreed with Lambo that Reborn is becoming more protective than a certain Storm guardian.

**_Office_**

**_Three weeks later_**

Tsuna, physically and mentally 24, is sitting in his office signing away paper works that contained a damage report of his two most destructive guardians. Hibari apparently, destroyed two mafia famiglias involved in an illegal drug trade while Mukuro destroyed yet another Estraneo branch around Italy.

He could not blame them after all. They destroyed something that should not even exist in this world, yet he just wanted them to somehow alleviate the damages they have done to lessen his headache.

A knock was then heard in his door as his storm guardian went in.

"Hayato?" Tsuna looked at the fidgeting figure, while glaring at the stacks of paper he was carrying. He let out a sigh.

"Mukuro or Kyoya?" He asked.

"Apparently, it's Reborn-san Tenth." His eyes went wide with surprise. Not that he didn't expect it, it's just that his former tutor has mellowed down a bit ever since he gave him a vacation.

"What did he destroy this time?"

"A boutique." Hayato bit his lip, not knowing whether to tell his boss or not.

"I'm guessing that the suit he ordered was not up to his expectations." Tsuna continued signing away. "Place the stack wherever there is free space."

"Actually, Tenth-"His boss looked at him. "He actually destroyed a store that sells clothes for women."

"My, my." Tsuna's eyes went wide. "It seems that a lady has caught his eye."

"What did I hear about Reborn having a girl kora?!" Colonello barged in the room messing up a few stacks of paper in the process. Tsuna suppressed a groan.

"Reborn-san has filed a complaint in a boutique in Paris because the clothes there were not up to his expectations." Hayato explained again.

"Reborn's got a girl kora?! Now this is news kora!" The former arcobaleno- now a teen – looked at Hayato with surprise.

"Why would it be a surprise?" It was Lal who went in. "Reborn's got a few girlfriends before Bianchi."

"Speaking of Bianchi, didn't she and Reborn broke up months ago?" Tsuna asked the trio.

"Aneki and Reborn-san broke up?!" Hayato shouted in surprise.

"Why didn't I hear about this kora?!"

"I was not aware of this."

"Didn't you notice?" Tsuna's hyper intuition flared up. There's something really wrong with the situation. "Bianchi rarely shows up compared before. Mom told me that she always asks advice from her and told me that she's going through some sort of a phase."

"Now that I think about it, Aneki rarely goes to Reborn anymore. More like she's avoiding him. She rarely cooks nowadays and is confined to her room more often." Gokudera shared his observations with everyone.

"Why did Reborn break up with Bianchi kora?!"

"Less questioning and more training you idiot!" Lal kicked Colonello on his head. "You're causing Tsuna more stress!" She motioned to the mess he made in surprise.

"That hurts kora!"

"Want to have a fight?!"

They simultaneously readied their rifles at each other.

"The training room is open you know." Tsuna reminded them. In case that they will heed his words. Not.

"Reborn! You're back already?" Tsuna greeted his tutor who is sipping on expresso at the kitchen. He managed to hide his surprise on seeing his tutor salivating the heavenly bitter drink as Tsuna would describe it.

"Skipping paper work again I see Dame-Tsuna." Reborn grinned. Tsuna spluttered.

"I do not!" He massaged his nose and headed towards a cabinet. "Takeshi wanted some tea after his mission, Lal-san wanted some hot chocolate and Colonello wanted some expresso." Tsuna grimaced.

"Vongola Decimo, reduced to being a butler. What would Vongola Primo say?" Reborn smirked. Tsuna noticed the odd behavior that the hitman portrayed but kept his silence. His intuition was telling him that the hitman was hiding something yet he disregarded it.

The comfortable silence which enveloped the duo for a few minutes was then interrupted by someone opening the door with a bang.

"Reborn! You're back kora?!" Colonello appeared, taking his seat near the teen. Tsuna gave him his expresso and he gladly took it.

"What's with this that they are telling me kora! You're having a new girlfriend kora?" Tsuna nearly burned his hand in the kettle in surprise.

Reborn continued on drinking his expresso, neither denying nor agreeing.

"You're cheating on Bianchi kora!" Colonello accused and pointed a finger at him. Tsuna sweat-dropped.

"That's it. Training room, B7 immediately." Reborn stood up swiftly and petted Leon on his hand.

"I will beat you kora!" Colonello pointed at him once again before running off.

Reborn stopped at the door. "If you're thinking about it, I am not cheating on Bianchi. We broke up a few months ago." He left swiftly.

Tsuna looked at the retreating figure, pondering on his tutor's odd behavior. Why explain to him though?

His HI is telling him to find out the cause for Reborn's distress. It must be big enough for the hitman to act odd. He is becoming more worried for his tutor. Reborn's known for keeping secrets. Everyone is entitled to have secrets, but he would go as far as to actually hide his injuries. Even a bullet wound.

Tsuna gritted his teeth. For the sake of finding out a secret, even though a bullet might be planted in his brain, he must do his utmost best to retain secrecy lest he'll die in a gruesome way.

Let's just say that Tsuna is not the very best to send during undercover missions due to the fact that he sucks at hiding or even diminishing his presence. In fact, Mukuro and Takeshi is perfect for undercover missions. Takeshi could pass off as a nearby bystander with the smile of his. Mukuro added with mist flames is a complete disaster.

Reborn raised an eyebrow at his no-good student who was attempting to hide himself behind a potted plant.

He continued monitoring a new target of his who is entering a newly opened café. The target managed to get hold of a blueprint containing Vongola's latest technology. Knowing Spanner and Shoichi, it is actually very hard to bypass their security. It was a trap laid down by the hitman himself.

He found out that one of them under Vongola is trading secrets with a well-known famiglia that is not even threatening to the family. Knowing that the mission could easily be handled by any of the guardians, Reborn had took the liberty in handling it despite it being an easy mission.

He despised traitors. Any threat to his student's life equals to a certain doom. He never had felt this way before. Pledging himself to Vongola was one of the things he never expected to do. Seeing his student being timid growing into such a fine young man caused him immense satisfaction. This was nothing compared to days he was tutoring Dino. Even he does not know what he is experiencing.

After a few hours monitoring the target, he could hear snores from the position of his student. He shook his head and went behind the pot. Tsuna is curled up into a ball, snoring. You could see the tiredness in his eyes. Reborn deduced that he must have pulled an all-nighter.

His eyes softened and easily lifted up his student. His face marred a frown when he realized that Tsuna became lighter than last time he saw him. He mentally took note to tell the cooks to largen the portion of his student's meal.

After lifting his student back to his own room, Reborn started to feel immense pain. He stifled back a gasp and hurriedly went to swallow some painkillers in his own room. He sighed in relief when the pain subsided down. Looking at the monitors, he felt a strong urge to kill someone. He grabbed his tie and woke up Leon from his sleep.

Damn monitoring. A clean shoot in the head will do the trick.

Tsuna felt a headache coming when Hayato brought another stack of papers during in the afternoon.

"I've finished some of the papers Tenth! Some of them needed your signature concerning alliances but some of them went to the shredder right away!" Hayato grinned as he greeted Tsuna who managed to give him a smile.

"Thank you Hayato but the stack is for? Don't tell me its about Mukuro and Hibari again." Tsuna replied.

"Tenth, it's from Reborn-san." Hayato sweat-dropped.

"Just place it somewhere Hayato." Tsuna shakily gave him a thumbs-up as his righthand man cheered for him before going outside.

Tsuna sighed in exasperation as he tried to find out what Reborn is hiding from him. A day ago, he woke up in his room with no recollection on how he got there. His last memory was watching Reborn monitoring his target. His HI was telling him that it was Reborn who carried him here but he refused to believe that.

Why would Reborn carry him in the first place? He would usually would be waked up with a hammer in his face but for the first time, he actually woke up peacefully. Something was really wrong with him. He even found some painkillers in Reborn's room but he refused to confront him about it. He was afraid of what would be his reaction.

He was afraid to know the truth. Reborn dying pervaded his thoughts and he became mortified. Reborn was his tutor, and sort-of a father figure to him. Sure, there were times that his tutor was odd, but he refused to ask unless it was the hitman who opened up to him.

He gritted his teeth as he chased those thoughts away. It was unhealthy of thinking something bad will happen. He assured himself that he'll give Reborn one more day before confronting him. This was the only thought in his mind as he went back signing to treaties in his table.

A loud knock on his office door made Tsuna open his tired eyes.

"Come on in." He directed and a fidgeting maid entered. "What can I do for you?"

"Signore Reborn told me to give this to you Decimo." The maid carried in a tray with a mug of coffee. An alarm went off in his mind. His sleepy state vanishing, senses became more heightened and he became poised for danger.

'What a feeble attempt to assassinate me.' Tsuna thought to himself. He decided to humor the fidgeting maid and grabbed the mug. He could see her eyes widened with glee as he smiled back to her, still acting sleepy. The mug was a few inches from his mouth when the door slammed open.

"Reborn?" Tsuna asked confused. His tutor had a poker face but Tsuna learned from the best in reading expressions. It was miniscule, but Tsuna managed to catch a shocked and panicked expression from his tutor before vanishing into a poker face.

"Don't drink that coffee Dame-Tsuna or I'll send you back to spartan training." Reborn threatened. He did not why he felt that way, but when he saw that the mug was inches away from Tsuna's mouth made him boil in fury.

"I won't Reborn. I was just humoring the poor kid." Tsuna smiled, a bit more gleeful than expected. The poor maid became pale as white as snow and froth began to cover her mouth. She choked and fell to ground with a pained expression on her face.

"Is she dead?" Tsuna asked Reborn who approached the still maid. Reborn nodded.

"I apologize for not informing you sooner. This is the last feeble attempt of the Picasso family from murdering you. I thought I had it all covered yet I forgot that there was one more traitor left." You could feel the disdain radiating off him when he said the word traitor.

This is not like him at all. He used to be in control of everything. He is meticulous and quick-witted. How could he let something as simple as this slip through his mind? He clenched his fist.

"Reborn?" Tsuna's voice made him snap back to reality. "It's fine. Nothing bad happened to me really." He tried to assure him.

"This was due to my incompetence. Give me a punishment Decimo." Reborn said with finality in his voice. Tsuna could see terror slip in his poker face.

"My hyper intuition could handle things like this so it's really no problem." The grip in Reborn's clenched fists produced blood. Tsuna looked at him shocked.

"Punish me Tsunayoshi." He gritted. Calling him Decimo means serious business, but calling him Tsunayoshi means that this was final. No arguments allowed. The pride of the hitman shatters every time Tsuna tried to reassure him. He would not allow incompetence in his line of work. He could not get Tsuna killed. No matter what.

"Fine." Tsuna pinched between his eyebrows, fighting back a growing migraine. "Tell me your secret."

Tsuna would have whooped in glee when he finally saw his tutor having a shocked face but decided that it was not the best situation. It was an accomplishment really.

After a few minutes of contemplating, Reborn managed to squeeze out a small agreement before going out of the office.

Tsuna stood shocked in his place at the words Reborn said.

_"Meet me at my room at 7pm unless you want to die in curiosity."_

He managed to calm himself and thought if it was a good idea of asking something personal.

"HEY KORA!" Colonello slammed his door open and messed up another stack. "WHAT IS THIS KORA?!" He asked motioning to the dead body on the floor.

"I will brew your expresso. Just please get rid of the body."

Tsuna gulped as he contemplated to knock on Reborn's door. He is terrified to know what was happening. The thought of Reborn dying echoed repeatedly in his mind. He wants to prolong it further,but he knew that he could not keep his tutor waiting.

He knocked on the door. Thrice.

Reborn's baritone voice of agreement made him gulped in sheer terror. He slowly opened the door and what greeted him made his eyes widened and he fell down on the ground with a loud thump.

Sawada Tsunayoshi fainted.

Tsuna opened his eyes to a blinding light. He opened his eyes and saw that he was in Reborn's room. His eyes widened as last night's events hit him with full force.

"Good morning Dame-Tsuna." Reborn greeted him. He- no he should probably get used to it- she was a knee-length dress and is standing on a nearby window.

Words could not leave his mouth as he saw an impossible sight. Is this another prank of Mukuro? Probably not because his HI was telling that all of this is real. Reborn is a girl. This is reality.

"Why did you destroy the boutique in Paris?" Of all the questions he could have asked, he did not know why that was the first thing that popped into his mind.

"They told me that they sold high-quality clothes. High-quality they said. It was clearly a low-quality." She snorted. "I expected you to ask why I am a girl first. You are still no-good Tsuna after all." He blushed.

Being insulted by a girl with this high degree of looks made him embarrassed. She still retained her curly sideburns and her short hair, but Tsuna could now see clearly her feminine features. Her long eyelashes (He once complained how Reborn's eyelashes looking too feminine), that ample bosom in her chest (he blushed fiercely at the thought) and all the other details he had not seen before.

Looking at Tsuna's inquiring gaze made her grin. "Make up is the best answer Dame-Tsuna, in case you were wondering."

He spluttered before regaining his calm. Not fully, but he is trying his best.

"Are you really a girl?" He asked.

"Biologically, yes."

"Then why?" He asked her. A shadow loomed in her eyes.

"Because I had to get revenge for my older brother. I had to kill that traitor who killed him. I had to be a man for the mafia does not widely accept women." She continued with a poker face but Tsuna could see the rage and fury in her eyes.

That explained her fury for traitors. The puzzle pieces were coming together. But there was still one thing boggling his mind.

"Why did you have some painkillers then? Are you hurt anywhere?" He swore that could he see a faint blush in her cheeks.

"I am not hurt anywhere Dame-Tsuna." She grinned. The wave of pain came back to assault her. "Call Viper. Now." She managed to squeeze out. Blood stained the sheets.

Seeing the blood made Tsuna panic. "I think I should call Dr. Shamal instead." His hands were shaking as he hastily tried to call Shamal.

"Please. Just call Viper." She asked with exasperation on her voice. Tsuna immediately nodded and ran out of her room. His first thought was the dining room, knowing that everyone gathered for breakfast.

"Viper!" His voice made everyone stop in the dining room.

"Is everything okay Tenth?" Curious gazes were sent along his way. He did not mind answering as he stalked over to the illusionist.

"Reborn needs help. Immediately." Viper looked at his frantic eyes before resigning to her fate.

"You'll pay me this time Vongola." Viper said before leaving the room.

The room was then filled with frantic questions asking if the hitman was alright, and questions he could not decipher.

With all the ruckus, he managed to make sure that Reborn's secret was not to be known by anyone. He did not let out a single word of their conversation. It was a secret between him and her.

Every time they pass by each other, they had a knowing look on their faces.

Tsuna still despaired at the amount Viper took from his bank account. It did not even make a dent but he was actually scared at Hayato who manages their finances. Not that he'll every get mad at him.

Reborn just grinned at his expense.

**_A/N:_****_Trivias_****_1\. Colonello started to drink expresso to show that he is equal to the hitman, even drinking the same drink as him._****_2\. Reborn's name is Renata. Her older brother is also related to the mafia, but because of a traitor, her older brother died in a warfare._****_3\. Reborn is experiencing actually what women experience during the start of their puberty. *wink wink_****_4\. Viper is a woman in this fic and is the only person in the Arcobaleno except for Luce who knows Reborn's secret._****_Reborn's feelings towards Tsuna is up to you readers to decide._****_This was supposed to be uploaded last October 13 during Reborn's birthday but I only managed to finish this tonight._****_The ending was kinda rushed because I wanted to leave it at that._****_The characters might be OOC, especially Reborn, so I'll apologize in advance._****_Criticism is welcome, and reviews are highly appreciated._****_Cover photo is not mine. KHR is also not mine. The plot is mine._**


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